The objectives of this study are to document the natural history and determine if the photocoagulation treatment is useful in the management of branch vein occlusion and its complications. The treatment by argon laser photocoagulation will be evaluated for the management of a) major branch vein occlusion without neovascularization, b) major branch vein occlusion with neovascularization, and c) macular branch vein occlusion with macular edema and decreased vision.